Integrated circuit chips and similar devices are commonly mounted or "packaged" in or on insulating bodies of ceramic or plastic and the terminal areas of the chip are connected to conductors on or in the insulating body. These conductors extend to the edge portions of the chip carrier body and have contact zones on their ends. Electrical connections are made to these contact zones by means of a chip carrier socket which has a recess which receives the chip carrier and which has contact terminals therein which engage the contact zones of the chip carrier. The terminals in the chip carrier socket in turn are connected to other conductors such as conductors on a ceramic substrate or a circuit board when the socket is mounted on the substrate.
The majority of all chip carriers are manufactured in accordance with an industry-wide standard referred to as the JEDEC Standard which was issued and is maintained by the Electronics Industries Association of 2001 Eye Street, N.W., Washington, D.C. 20006. This standard sets forth specifications for the dimensions of the chip carrier body, the locations of the contact zones on the chip carrier, and the manner in which the chip carrier will be precisely positioned in the chip carrier socket so that any manufacturer can produce sockets or chip carriers which can be interchanged by an equipment manufacturer. In accordance with the JEDEC Standard, the chip carrier body is square and has one beveled corner and three notched corners. The chip carrier socket has a spring device which bears against the beveled corner of the chip carrier body and urges the corner which is opposite to the beveled corner against a pin on the socket body. The pin is seated in the notch at that corner. Pins are also provided for the remaining two notched corners of the chip carrier body with some clearance in these remaining two corners so that some differential thermal expansion can take place when the chip carrier and socket are placed in service.
The system described above of using a spring and locating pins on the socket for locating the chip carrier is satisfactory if the contact zones on the chip carrier are located on centers spaced apart by about 0.020 inches (0.51 mm). However, if the contact zones are spaced apart by only 0.010 inches (0.25 mm), contact between the contact zones of the chip carrier and the terminals of the socket may be lost if there is differential thermal expansion of the chip carrier relative to the socket. This loss of contact would result from the fact that one corner of the chip carrier is fixed by virtue of the locating pin which is snugly seated in the notch of that one corner and if the chip carrier should undergo thermal expansion to a different extent than the chip carrier socket, the contact zones of the chip carrier may be moved away from the contact terminals of the chip carrier socket. The present invention is directed to the achievement of an improved locating system for chip carriers and chip carrier sockets which will greatly reduce the effects of differential thermal expansion and thereby eliminate the possiblity of loss of electrical continuity. The JEDEC standard is inadequate for an emerging generation of chip carriers having contact zones on very closely spaced centers; the chip carrier and socket of the present invention will satisfy the requirements of this new generation.